Manufacture of artificial silk and the like from viscose solutions



Patented Oct. 26:;19 26.

UNITED STATES PA gsNT oFFlcE.

I *wnmmfi ron'rnn nnnnrnn, or nnmrsrnan HEATH, nonnon nnsnann.

MANUFACTURE OF ARTIFICIAL SII IK AND 'IHIE L IKE FROM VISCOSE SOLUTIONS.

Io Drawing. Application filed August 31, 192 5, Serial 11 0. 53,748, and in Great Britain September 17,11324.

( This invention relates to an improved chess for the production of artificial yarn of the kind in which the filaments are dried in the skein form underftension in the gel 6 condition so as to cause them to adhere tem- Q porarily to each other in such a manner as'to resemble what is known as.raw or gum natural silk, and my said invention has for.

its object to produce such artificial gum .10 ilk yarns from viscose solution.

In the treatment of viscose artifical silk it is necessary to remove the sulphur. from :the freshly spun filaments. This treatment has heretofore taken place after the 15 filaments have been washed and dried under tension-on astretching-frame so that they I are no longer in a gel condition,-since it has been found that the desulphurizing solution consisting e. g. of sodium sulphide with possibly some free caustic soda in it, is iable to'increase the hydration of the fresh; unfilaments and thereb reduce their anical stren h so that 1t is not prac En ma-to desulp urize them and then dry;- them under tension whilst still in the *gel condition. y

Accordin to my invention, in order to I enable the aments to be desulphurized or if desired fiesulphurized and bleached, or both ble ched and d ed, in the gel condition and the dried un er tension, the freshly drie are treated with a delsulphurizing solution to which there is added not less than440 per cent of the saturation value at normal atmospher'c temperatures of a 1 suitable salt or sal s (i. e. any soluble salt ."other than 'the sulphide) of an alkali metal or metals, (i. je.; sodium, potassium, or

For example, sufficient comfmon stilt is' added to bring the concentration :offthe bath np-to 80 per cent of its saturatioii value respect to such salt. With concentratifi of salt substantiall less'than the 4Q nt above mentione the file"- ments are unable to withstand the tension neeessaryto beapplied-during drying. It is an advantageto make a similar addition of a salt ors'alts of an alkali metal or metals to. the dyein ,ThleachiniZ and other baths through whicfithe threa desulphurized as above described are subsequently passed.

-When an addition is made it 1s not nec- 4 essary, owingfito the relatively milder conchrecgiitated gel filaments, before they are tions obtaining in the treatment, to add such a large proportion of salt. In some cases a proportion as low as 10 per cent of the saturation limitis found to give beneficial results. Moreover e. g. in cases where the dyeing takes place in aesodium sulphide so lution, the desulphurizing and dyeing may take place simultaneously, provided the d eing action be not prevented by the saltmg out of the dye stufi.

By this means, the filaments are prevented from being further hydrated during their exposure to the action of the desulphurizing .and other (e. g. bleaching or dyeing) baths, and thus their mechanical strength is preserved or ev .increased so as to enable them to be drie ider .tension in the gel condi; tion in er to produce artificial silk of the gungi typefliavingthe filaments adherin g together.

Also while the filaments are still in the the final wash water, which may or may not contain added soluble salts, this watergel condition and ready to be immersed in wtemperatureor both as to enable it to remove the added dressing material or size.

. B the means explained a viscose product canbe obtained which'very closely resembles raw silk, and this is found to beef particular advantage where fine denier yarns consisting offine denier filaments are required." There is also a saving in the cost producing artificial.-

before the are dried in a state of tension,

are,treate 1 with a desulphuriiing'so u ion to which there is added alkali metal salt in i i amount not less than 40 e1 cent ofthe satv urat-ion value at norma atmospheric temperatures. I

2. A process of producing artificial filaments and yarns in imitation of gum type silk wherein the freshly precipitated gel laments produced from'viscose solutions before they are dried in a stateof tension, are treated with a desu'lphurizin'g solution to which there is added common salt in amount not less than 40 per cent of the saturation value at normal atmospheric temperatures.

3. A process of producing artificial fila-- ments and yarns in imitation of gum type sill; wherein the freshly precipitated gel filaments produc from viscose solutions before they are ied in a state of tension, are treated with-a desulphurizing so-' lution to which there is added common salt the amount of which is substantially 80 per cent of the saturation value at normal atmospheric temperatures.

4. A process of producing'artificial filaments and yarns in imitation, of gum 25 type silk wherein the freshly precipitated gel filaments produced from viscose solutions, before they are dried in a state of tension, are treated with a desulphurizing solution to which there is added suitable al 30 kali metal salt in amount not less than 40 per cent of the saturation value at normal atmospheric temperatures, suitable salt of an alkali metal being also added but in a smaller proportion .to baths which are additional 35 to the desulphurizing bath and with which the filaments are treated whilst still in a gel condition.

.WIVLLIAMPORTER DREAPER} 

